Display device



May l, 1945.

FQL

W. H. BOHLKE DISPLAY DEVICE vFiled Nov. 50 1940 2 Sheets-Sheet 1 NEGLIGBLE ZERD HDJ. OHMS DJ.

f4 Q N UNMS ILC. C0 N D-C. VOL'TS 0 G May 1,1945. -w. H, BOHLKE DISPLAY DEVICE Filed Nov. 50, 1940 E ,2.

2 Srheets-Sheec 2 Snventcpr willig/mii. BofLI/' Patented May l, 1945 DISPLAY DEVICE william H. Bobike, oak1yn,N. J., signor to Radio Corporation'of America, a corporation of Delaware Application November 3o, 1940, serial No. 367,899

2 Claims.

This invention relates to advertising display devices, and has for its principal object the provision of ,an advertising display particularly adapted to promote the sale of electrical measuring devices. v

The invention will be described in its application to a vacuum tube volt-hmmeter, but may be employed to equal advantage in connection with many other types of measuring instruments, particularly those which may be used to make a number of different types of measurements throughout a wide range of values. The voltohmmeter is typical of this class of instruments since it combines in one instrument, for example, an indicator for measuring direct. current voltages from zero to 1000vo1ts, alternating voltages from to 1000 volts, and values of resistance from zero up to several hundred or even a thousand megohms.

Of prime importance 'to the prospective .pur-v chaser of such instrument is its accuracy; and this involves not only the accuracy of calibration at given points, but also its readibility, Which, in turn, depends on the linearity of the indicator scale, thev number of separate voltage orv resistance ranges used. The prospective purchaser also wants to know the sensitivity and range of', the instrument. He will ask how small a voltage will it measure? For instance, can itmeasure the voltage of a bias cell? Can itbe used to measure, say, the resistance of a coil?,` Can the leakage resistance of a capacitor or insulating material be measured? The prospective purchaser will also know that the input impedance of the instrument must be extremely high, particularly where it is-to be used in testing radio circuits, since it is well known that an accurate measurement can be made only when the impedance of the measuring instrument is high with respect to that of the source across which the voltage appears. A n

The instrument being advertised may also have other advantages which may not occur to the prospective customer. For example, the instrument may include inherent protection or special protective circuits such that the meter cannot be damaged upon application of a voltage far in excess of that for which ythe instrument is set.

Thus, if the range selector is set for the measurement of voltages from 0-3 Volts, and 300 volts, for exam-ple, is accidentally applied, will the instrument be damaged or will the protection afforded automatically prevent injury? These typical questions, land others, are, of

course, answered by any printed advertising matter used to promote the sale of the-instrument. In accordance `with the present invention, however, an advertising display is proposed which not only points out the advantage and features of the instrument, but also makes possible an actual personal-a try it yourself typedemonstration which will convince the customer of the advantages of the instrument. Thus, each display in the distributors and/or dealers show room'advertising the volt-ohmmeter, for example, has mounted thereon and connected toeonvenient terminals, various electrical elements including resistors, capacitors, inductors, k and sources of direct` and alternating voltage sothat tests may bemade in', accordance `with printed instructions--a part of the display--Which dem- `onstrat'e vividly theactual operation of the-indisplay, and Figure 2 is a rear view-of the same display. Similar reference numerals referto similarelements throughout the several figures of the drawings.

Referring to the figures, reference numeral 3 is, for example, a plywood, metal Aor heavy cardboard panel having a conveniently located aperture 5 which is cut out so as to receive the voltohmmeter 1, or other instrument. 'I'he instrument I which may be heavier than an ordinary meter is supported in the aperture 5 so that its face is approximately flush with the .panelby means of a shelf 9 extendingrearwardly 'from the panel. The shelf and panel-are supported by one or more supporting members I I which are at right' angles to the panel and to which the panel and shelf are fastened.' i

Suitable advertising matter is printed on the face of the panel. To make a pleasing symmetrical arrangement, this matter may beV within distinctively colored sections I5, I1, and I9, for example. Thus, the features ofy the instrument for measuring D.C. voltage are listed insection I5 immediately above the circuit'elements provided for proving them. The `features relating to the measurement of resistance areset forthin section I9 immediately above the circuit element provided for proving these features.

While the Volt-ohmmeter 1, per se, is not a part of the present invention, it will be described briey. Three input terminals are provided, one,`

4, for use when measuring resistance and alternating current, a second, 6, for use when measuring direct current voltages, and a third, 8, common to both. The common input terminal 8 isl connected to the case of the volt-ohmmeter and therefore to ground. A toggle switch I turns the instrument on, and a pilot light I2 indicates that the device is operating.

Two selector f'switches are provided, 'the first,

- I 4, being a conventional attenuator-'or multi` plier switch provided with a suitable scale indif cating the multiplication factor to be used in determining the actual voltage or resistance from the meter reading, and the. other, I6, being used to select the type of measurement.tov be made, lsuch as ohms, A. C. Volts, or D.-C. volts; Two positions for the latter. measurement are provided, one marked volts andthe other connections, thus making it unnecessary to change the test. prods when the meter reads back-lwards due to improper polarization, Potentiometer controls I8 and 2,0 are provided for the adjustment of the meter zero for thevoltage and resistance scales, respectively.`

. Below the instrumenta small' battery 2l ofthe bias cell type and a 1 megohm resistor 23 are mounted within a distinctively colored section 25, The leadsl from the bias cell holder 21 and the resistor are connected to terminals 29, 3l and 33,1 preferably' by connections at the rear. of the panel. One lead 63 from the bias cell is cone; nectedv to the lower terminal 33,"the.other 65 to the terminal 3l to which one end of. the resistor is also connected yby a lead y61.*"The remaining terminal 29 is connected to the other end of resistor 2'3.

, printed and suitably located on display for making various tests which demonstrate the merits of theinstrument. For example, he is directedto check the input impedance by measuring the voltage of the cell 2l by connecting the instrument leads directly across the cell terminals 3l, 33, noting the voltage With the instrument-set on `the proper scale, and then measuring the voltage tlifroughthe 'lgmegohrrf'rfesistor 23 Yby connecting theA test prod. toterminalZS. If the voltage is the same as before' orsubstantiallyso, he will be convinced that the input impedance of the inf is;

volts, which effectively reverse vthe input?4 pared to that ofthe resistor.

The prospectiveY customer may also be directed toy test theresistance measuring ability of the instrument by measuring the very low resistance of the coil 31,'and the very high resistance due to the leakage in capacitor 39. A permanent leakage value may be secured by assembling a very' high carbon resistor or resistors within the capacitor roll. The A.C'.`range andi the high DL-C. range mayjalso be checked by touching/or plugging in of the proper test prodsltoA the proper terminals of the rectier. He mayithen be directedto settthe selector switch of the meter at f the .most sensitive position and itouchthe test prod tothe high voltage terminal. If `the instrumentz meter isas claimed, of course, if will'not be damaged, although the' needle will? undoubtedly bedeflected oiT scale. VvTo make necessary mov'- ingonl-y' one test prod, a" common. groundflead 11 tiesr terminal 33 with terminal' 55'..

. Actual operating, demonstrations are farinore convincingy .than -mere claims. Other tests may bemade, of course, to` demonstrate other features, the nature of the demonstrationbeingdetermined by the;A nature and capabilities of -the:` instrument. For example, a paritial or complete radio-circuit may b e provided, including radio frequency `and audio frequency voltages'.todemonstrate thev frequency range of the instrument and its utilityin testing radidfreceivers Cathode ray oscillobols for the vcoil and capacitor are printed on the panel toV show their actual connection.

y Stil-l another suitably colored section 49l vcontains. the circuit. diagram of a transformer and v rectifier connectedf in a rectifying circuit. The

Voltagecircuits: are preferably insulated pin' jacks towhich connection can` only bemad'eby probes 81a, BJ-bvsuppled with the instrument and con-` nected thereto byy leads 83a, .8312V The other terminals may;l be convenient-.typeof4 lug, bolt or jack. i

The display panel; andinstrument areplaced.. so as. tov be. available to thev prospective customer.`

By suitable words. on,.the panel: he is invited'to try. it. for himself, and; specific directions arel graphs, Wheatstone bridges, frequency meters,

signal tracing equ-ipn'ierity and other` measuring and indicati-ng devices.l may be advertised `similarly by providing operating. tests in Vconjunction' tests. himselfwhich will bemore convincinglthanV mere claims.

` I clairn as my invention: l 1. An advertising display fora ;voltohmmeter comprisingv a panel having an aperture therein, a

rearwardly extending'bracket for 4supporting said meter within` said aperture, a plurality of diiferof said elements whereby said meter may be` tested readily by measuring the properties ofsaid elements, f 1

2; advertising display for a 'voltoh1'nmeter comprising a display panel, nfie'ansufjor mounting.

said bolt-ohmmeter-onv said; panel', Va bracket `for supporting the voltohmmete'r, a` "source 'of low voltage direct current and a high impedance serially connected and mounted on said panel, terminals for'making electrical connection to said source and said impedance, a source of alternating current of selectable voltage mounted on said panel and terminals for connection to said source whereby the operation of said volt-ohmmeter may be tested, and schematic representations on the WILLIAM H. BOHLKE. 

